Solar drying experiments of maizes were conducted at Gape- Kpodzi, in southern Togo. In this purpose, new type tunnel solar dryer was used. Solar dryer consist of an air collector, drying chamber and an air circulation system. Heated air... more
Solar drying experiments of maizes were conducted at Gape- Kpodzi, in southern Togo. In this purpose, new type tunnel solar dryer was used. Solar dryer consist of an air collector, drying chamber and an air circulation system. Heated air in solar air collector was forced through the maizes by a blower. Yellow dent type maize was used for drying experiments. During the drying period, drying air temperature, relative humidity, air flow rates, solar radiation, and lose of mass were measured continuously in different levels of the dryer. Maize with initial moisture content of 0.37 dry basis (kg water / kg dry matter) were dried until they reached a final moisture content of 0.13 (kg water / kg dry matter) at different temperatures with respect to solar radiation variation. Drying time was examined with moisture content ratio as exponential and polynomial correlations. The effective diffusivity varied from 1.938x10-10 to 1.164x10-10 m2/s over the different level of temperature range. Fou...
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A platform of collaborative work is a centralizing tool of information related to the conduct of a project or a collective mission. The collaboration allows project participants to work together by sharing information, processes, and... more
A platform of collaborative work is a centralizing tool of information related to the conduct of a project or a collective mission. The collaboration allows project participants to work together by sharing information, processes, and common values. On the other hand, free software provides powerful applications ready to be integrated for the construction of applications and internal platforms to the
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Poly(N-vinylcarbazole) (PVK) powder has been doped by bromine at room temperature and also at 370, 420 and 470 K for 24–72 h. It is shown, by electron spin resonance (e.s.r.), optical absorption, X-ray photoelectron spectroscopy (XPS),... more
Poly(N-vinylcarbazole) (PVK) powder has been doped by bromine at room temperature and also at 370, 420 and 470 K for 24–72 h. It is shown, by electron spin resonance (e.s.r.), optical absorption, X-ray photoelectron spectroscopy (XPS), that a charge transfer complex (CT complex) is formed between PVK and Br. However, some bromine is found to react with PVK, even after doping at room temperature, by addition or substitution, since not only bromine anion, which evidences the presence of the charge transfer complex, but also neutral bromine, has been detected by CPS. After heating, our results show that PVK is transformed into a new, more insoluble polymer. This polymer is amorphous, while some traces of carbazole and NH4Br are present in the powders. The increase of the conductivity is probably related to the formation of some π bonds in the new amorphous polymer.
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ABSTRACT The properties of molybdenum trioxide (20 nm)/silver (x nm)/molybdenum trioxide (35 nm) multilayer structures, deposited by simple vacuum evaporation, depend significantly on the deposition rate and on the thickness of the silver... more
ABSTRACT The properties of molybdenum trioxide (20 nm)/silver (x nm)/molybdenum trioxide (35 nm) multilayer structures, deposited by simple vacuum evaporation, depend significantly on the deposition rate and on the thickness of the silver layer. If the presence of a commutation from an insulating state to a highly conductive state in these structures is usual, we show that, the thickness of the layer of Ag corresponding to the percolation of the metal paths, decreases from 8 nm to 4 nm when the Ag deposition rate increases from 0.2 nm/s to 0.4 nm/s. The transmission being optimum at 10-11 nm, the calculation of the factor of merit shows that the best structures are obtained for silver films approx. 10 nm thick deposited at a rate between 0.3 nm/s and 0.4 nm/s. When the optimal structures MoO3/Ag/MoO3 are used as anode in planar organic solar cells anode/Cul/CuPc/C-60/Alq3/Al they allow achieving power conversion efficiency of the same order of magnitude than that achieved by reference cells using ITO as anode.
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ZnO thin films have been deposited by chemical bath deposition (CBD-ZnO). The deposition conditions, i.e. the pH and the temperature of the bath, have been adjusted to achieve the deposition of porous, but adherent, thin films. After... more
ZnO thin films have been deposited by chemical bath deposition (CBD-ZnO). The deposition conditions, i.e. the pH and the temperature of the bath, have been adjusted to achieve the deposition of porous, but adherent, thin films. After annealing in air half an hour at 300 °C ZnO films crystallized in the hexagonal structure are obtained. They are nearly stoichiometric with
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ABSTRACT ZnO thin films deposited by chemical bath deposition (CBD) have been studied using x-ray diffraction, scanning electron microscopy, electron microprobe analysis and electrical measurements. The optimum CBD conditions for... more
ABSTRACT ZnO thin films deposited by chemical bath deposition (CBD) have been studied using x-ray diffraction, scanning electron microscopy, electron microprobe analysis and electrical measurements. The optimum CBD conditions for achieving structured, but adherent, ZnO films are as follows. Zinc acetate (0.0188 mol l−1) and ethylenediamine (0.03 mol l−1) are mixed. The pH of the bath is raised by addition of a base (0.5 mol l−1, NaOH). The solution is maintained at a temperature between 60 °C and 65 ° C, while the bath is continuously stirred. We proceeded to anneal in room air for 30 min at 300 °C and under vacuum for 2 h at 300 °C. All the films obtained are nearly stoichiometric ZnO films crystallized in the usual hexagonal structure. As expected the films are rough and porous. The main difference between the two ZnO film families is their conductivity. The conductivity of the films annealed under vacuum is five orders of magnitude higher than that of those annealed in room air.
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An original surface passivation technique of indium tin oxide (ITO) used as anode in organic solar cells is proposed. We demonstrate that a thin MoO3 film (3.5+/-1 nm) at the interface ITO/organic donor allows improving significantly the... more
An original surface passivation technique of indium tin oxide (ITO) used as anode in organic solar cells is proposed. We demonstrate that a thin MoO3 film (3.5+/-1 nm) at the interface ITO/organic donor allows improving significantly the devices' performances. The devices are based on the multiheterojunction structure copper phthalocyanine (CuPc)/fullerene (C60)/aluminum tris(8-hydroxyquinoline) (Alq3). The deposition of MoO3 onto ITO improves the charge transfer from CuPc to ITO. The enhancement in the hole collection efficiency in the presence of an oxide layer can be explained in terms of the reduction in the effective barrier against hole transfer from CuPc into the ITO anode. The contact ITO/MoO3/CuPc behaves like a metal-insulator-semiconductor (MIS) structure, which allows reducing the energy barrier due to the difference between the work function of ITO and the highest occupied molecular orbital of CuPc. It is shown that the optimum MoO3 thickness corresponds to a compromise between an optimum ITO coverage and a sufficient transparency of the trapezoidal barrier for the tunneling of the charge carriers. The MoO3 thin films are discontinuous, and the passivation effect is improved when the oxide thin film is covered by an ultrathin gold film. Such behavior is discussed in the light of band scheme structures after contact and of geometrical considerations.
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... L. Cattin,1 F. Dahou,2 Y. Lare,3 M. Morsli,4 R. Tricot,1 S. Houari,2 A. Mokrani,1 K. Jondo,3 A.Khelil,2 K. Napo,3 and JC Bernède4,a) 1Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP... more
... L. Cattin,1 F. Dahou,2 Y. Lare,3 M. Morsli,4 R. Tricot,1 S. Houari,2 A. Mokrani,1 K. Jondo,3 A.Khelil,2 K. Napo,3 and JC Bernède4,a) 1Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France ...